High-frequency repeater



March 10, 1931. J. L. wooowoRfH HIGH FREQUENCY REPEATER Filed April 12. 1930 Inventor: John .Woodwcn-t'h by MW His Attorney;

Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE JOHN L. WOODWORTH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC I COMPANY, .A CORPORATION OF NEW YORK HIGH-FREQUENCY REPEATER Application filed April 12,

My invention relates to high frequency repeaters, and it has for one of its objects to provide a repeater which is particularly adapted to repeat high frequency oscillations which are transmitted over the lines of the usual power distribution system for control purposes.

Another object of the invention is to provide a repeater employing one or more electron discharge devices which may be supplied with operating electromotive force of commercial frequency and which has greater output energy than may be had from discharge devices of the same rated capacity when connected in known repeater circuit arrangements.

A further object of the invention is to provide a repeater of the type indicated which is particularly adapted for repeating carrier current signals between power lines which do not permit of carrier signaling at the same frequency, the repeater being adapted to change the frequency of the repeated signals.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims.

My invention itself, however, both as to its organization and method of operation, to-

gether with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Figs. 1 and 2 represent diflerent embodiments of my invention.

Referring to Fig. 1 of the drawing I have shown at l a repeater for receving oscillations from an input channel 2 and for supplying oscillations of increased amplitude to an output channel 3. The channels 2 and 3 may be either the same or different lines of a power distribution system. The channel 2 is c0upled by means of coupling condensers 4 to the input circuit 5 of the repeater. In the same way the channel 3 is coupled through condensers 6 to the output circuit 7 of the repeater.

The repeater comprises an electron discharge device 8, the anode and grid of which are energized with alternating electromotive force supplied respectively from the sec- 1930. Serial No. 443,908.

ondary windings 9 and 10 of a transformer 11. This transformer may be supplied With electromotive force of any suitable commercial frequency as, for example, electromotive force derived from either of the channels 2 and The third secondary winding 12 on transformer 11 is utilized to energize the oathode of the discharge device and the midpoint of this Winding is connected to both of the inner terminals of the windings 9 and 10. Thus, by means of these windings the anode and grid are supplied with operating electromotive forces which are in opposed phase relation.

The anode circuit of the discharge device includes, in addition to the Winding 9, an oscillatory circuit 13 and a relay 14. The grid circuit includes a winding 15 and a tuned circuit 16. The winding 15 is coupled to the oscillatory circuit 13 and comprises a feed back coil whereby energy is fed from the anode circuit into the grid circuit thereby to cause the discharge device to produce oscillations having a frequency determined by the circuit 13. The output circuit 7 is also coupled to the winding 13, and hence oscillations produced in the circuit 13 are supplied to the winding 7 and hence to the outgoing channel 3.

The Winding 10, as previously pointed out, serves to cause the grid to be negative during the half cycle of the alternating current wave in which the anode is positive. The potential of this winding is sufficient noruiaily to prevent the production of oscillations in the tuned circuit 13. When high frequency oscillations are received, however, and electromotive force having a corresponding frequency set up across the tuned circuit 16, to which the input circuit 5 is coupled, this electromotivo force will partially overcome the effect of electromotive force of the winding 10, and thus trigger the device into oscillations, these oscillations being supplied to the channel 3.

As thus arranged the circuit may be adjusted to extreme sensitivity to received oscillations. That is, in response to a received signal of relatively small intensity the system may be triggered into oscillation, and

ill then supply high frequency currents of relatively large amplitude to the output circuit. The ratio between the amplitude of the input and output waves may be greater when the discharge device is connected in a circuit as described, than is the case with a discharge device having the same rated capacity connected in known circuit arrangements to amplify the received signals. The sensitivity of the system, however, is dependent to a certain extent upon the range of variations in the low frequency voltage which maycocour in any particular installation of the equipment.

ft may frequently be desirable in the operation of carr er current control systems to perform different control functions at remotely located points. In accordance with my invention a repeater of the type described may be located at one of these points having a relay 14.- included in the anode circuit of the discharge device. Zhen high frequency oscillations are received in the input circuit 5 and the device is thereby triggered into oscillations, the anode current of the discharge device substantially increases. The relay 1% may thus be adjusted to respond to this increase in anode current. This relay may be employed to perform any desired control function at the point at which the repeater is located. At the same time the high frequency oscillations produced will be su pplied to the outgoing channel 3 which may extend to the next point at which it is desired to produce a control operation.

It will be apparent that when the received high frequency oscillations are interrupted the oscillations produced in the circuit 18 will continue until the anode potential becomes negative with respect to the cathode or sufficiently diminished to preclude operation ofthe device, at which time oscillations will cease.

The oscillatory circuit 13 may be tuned to the frequency of the received oscillations, or to any other suitable frequency, as desired. Thus the device comprises a very convenient means for repeating from one distribution system to another where the characteristics of the two systems to not permit the use of carrier waves of the same frequency upon the two systems. When it is desired to control the output frequency accurately the circuit 13 may be tuned to a harmonic of the received oscillations or to some frequency with which the received oscillations are modulated. Since, due to the negative potential impressed upon the grid when the anode is positive, the device Soperates as a detector oscillations of a modulation frequency will be set up in the circuit 13 and supplied to the outgoing channel. In this way the frequency of the oscillations produced may be controlled within certain limits, dependent upon the tuning of the circuit 13, from the station at which the operator is located.

In the system shown in Fig. 1 it will be apparent that oscillations are supplied to the outgoing channel 1 only during that portion of the alternating current wave in which the anode is positive. In Fig. 2 I have shown an arrangement in which high frequency oscillations may be supplied to the outgoing channel during both half cycles of the alternating current wave. As shown in Fig. 2 the system comprises two electron discharge devices 17 and 18 having separate sources of electromotive force comprising the secondary windings of transformers l9 and 20. An intermediate point on each of these secondary windings is connected to the cathode. Opposite points on the secondary winding of transformer 19 are connected respectively to the two grids, and opposite points on the secondary winding of transformer 20 are connected respectively to the two anodes. The connection between the cathodes ofthe dis.- charge devices 17 and 18 and the intermediate point on the secondary winding of transformer 20 includes the relay 1 1 and the oscillatory circuit 13, this circuit being coupled to the output circuit 7 and also to the feedback coil 15. The coil 15 is included in the connection between the cathodes and the intermediate point on the secondary winding of transformer 19. This latter connection also includes the tuned circuit 16 which is tuned to the received oscillations and coupled to the input circuit 5. By means of the transformers 19 and 20 the anodes of the two discharge devices are energized in opposite phase and the grid of each device energized in opposite phase with respect to the respective anode. Thus when oscillations are received each device oscillates during the half cycle in which its respective anode is positive. nately thereby to supply high frequency oscillations to the channel 3 substantially continuously.

The cathodes of the discharge devices are energized through a transformer 21. The primary windings of the transformers 19, 20 and 21 may be supplied in parallel from a distribution circuit 22 which may in turn be supplied from the power distribution system over which the carrier waves are transmitted or received.

Where the channels 2 and 3 are parts of the same power line, a trap circuit 28, 24 is provided in each of the conductors of the power line to. isolate the two channels with respect to high frequency currents. These circuits may be tuned either to the frequency of the received or transmitted oscillations or to an intermediate frequency. These trap circuits, however, may be obviated where the two channels are connected by high impedance power apparatus such as a transformer VVhile'I have disclosed particular embodiments of my invention, it will of course be Thusthe two devices operate alterunderstood that I do not wish to be limited thereto since many modifications may be made, both in the circuit arrangements and in the instrumentalities employed, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

W hat I claim as new and desire to secure by Letters Patent of the United States is:

l. The combination, in a high frequency repeater, of an incoming channel, an outgoing high frequency channel, an electron discharge device having a grid, an anode and a cathode, a circuit between the anode and cathode, a circuit between the grid and cathode, a coupling between said circuits whereby said device produces high frequency oscillations, means for supplying to the grid and anode low frequency alternating electromotive force in opposed phase relation the grid potential having a value sufficient to prevent the pro duction of oscillations during the half cycle of the alternating current wave when the anode is positive, a coupling betwen the grid circuit and. said incoming channel whereby received high frequency electromotive force may be applied to said grid to overcome the low frequency electromotive force applied thereto thereby to cause said device to produce oscillations and a coupling between the anode circuit and said outgoing channel whereby high frequency oscillations are supplied to said outgoing channel.

2. The combination, in a high frequency repeater, of an electron discharge device having a grid, an anode and a cathode, a circuit between the grid and cathode tuned to a certain high frequency, a circuit'between the anode and cathode tuned to a different frequency, a coupling between said anode circuit and grid circuit whereby oscillations are produced by said device having said different frequency, an output circuit extending to a remote point arranged to be supplied with said oscillations of different frequency, means for supplying low frequency electromotive force to said grid and anode in opposite phase relation, the electromotive force supplied to the grid being suflicient to prevent the production of oscillations when the anode is positive, and means for supplying oscillations of said certain frequency to said grid circuit to overcome said low frequency electromotive force supplied to the grid, thereby to cause oscillations of said different frequency to be supplied to said output circuit when the anode is positive.

3. The combination, in a high frequency repeater, of an input circuit, an output circuit, an electron discharge device having a cathode, an anode, and a grid, a source of electromotive force having an intermediate point connected to the cathode and opposite points connected respectively in circuit with the grid and anode, a relay connected in the circuit including said anode and source of electromotive force, a coupling between the anode circuit and the circuit including the grid and source of electromotive force whereby high frequency oscillations may be produced when the anode is positive, the electromotive force supplied to the grid by said source being sufiicient to prevent the production of high frequency oscillations, a coupling between said input circuit and circuit including said rid and source of electromotive force whereby oscillations received in said input circuit are impressed upon said grid and to overcome the electromotive force supplied to the grid by said source and thereby cause high frequency oscillations to be supplied to said output circuit and operation of said relay.

4. The combination, in a high frequency repeater, of a pair of electron discharge devices, each of said devices having an anode, a cathode and a grid, a source of low frequency electromotive force, a connection between an intermediate point on said source and said cathodes and a connection between opposite points on said source and each of said anodes whereby said anodes are energized in opposite phase, a second source of electromotive force having an intermediate point connected to said cathodes and opposite points connected respectively to said grids, said sources of electromotive force being of the same frequency and having phase relation such that the grid of each discharge device is negative when the anode is positive, a coupling between said two connections between said intermediate points on said sources and said cathodes whereby high frequency oscillations of desired frequency are produced by said devices, an output circuit coupled to the connection between said intermediate point on said first source and said cathodes and an input circuit coupled to the connection between the intermediate point on said second source and said cathodes whereby when oscillations are received in said input circuit, the electromotive force supplied to said grids is overcome and high frequency oscillations are alternately supplied to said output circuit by each of said devices.

In witness whereof, I have hereunto set my hand this 11th day of April, 1930.

JOHN L. WOODWORTH. 

